The US railroad industry is one of the most onerously-regulated in the world. The federal government’s to blame. The
requirements that the feds have for running passenger trains at any competitive speed are utterly ridiculous; not only “track classes” but also signaling requirements, “crashworthiness” regulations that are absurdly high and not even all that practical.
At railroad crossings, the Federal Railroad Administration even requires that if you intend to run passenger trains faster than 110 mph and up to 125 mph, you have to put up something called an “impenetrable barrier” now (and there is no such thing as yet) or eliminate the crossing altogether. For faster than 125 mph, all crossings have to go.